Update V8 to r4851 as required by WebKit r61121

Change-Id: Ib01b7c8e38d5b82b254192fc06365aa5b85780c5
diff --git a/src/log.cc b/src/log.cc
index f48b358..ada73cb 100644
--- a/src/log.cc
+++ b/src/log.cc
@@ -1295,6 +1295,10 @@
         description = "A call IC from the snapshot";
         tag = Logger::CALL_IC_TAG;
         break;
+      case Code::KEYED_CALL_IC:
+        description = "A keyed call IC from the snapshot";
+        tag = Logger::KEYED_CALL_IC_TAG;
+        break;
     }
     PROFILE(CodeCreateEvent(tag, code_object, description));
   }